Thermal incineration unit

ABSTRACT

A thermal incinerator unit with an improved design that provides a gas recycle passageway means around and in combination with the combustion section to thereby limit the temperature increase through such combustion section and provide a controlled burning of the incinerated portion of the fumes. The recycle arrangement within the incineration unit is particularly applicable to the handling of a high B.t.u. content contaminated gas stream which could normally result in an excessive temperature rise across the combustion zone.

United States Patent lnventor Leslie C. Hardison Norwalk, Conn.

Appl. No. 31,961

Filed Apr. 27, 1970 Patented Sept. 14, 1971 Assignee Universal OilProducts Company Des Plaines, lll.

THERMAL INCINERATION UNIT 10 Claims, 3 Drawing Figs.

U.S.Cl 431/116, 34/155, 263/3 lnt.Cl F23l15/00 Field of Search 431/202,115,116,5,9;263/3;34/155 [56] References Cited UNITED STATES PATENTS2,224,544 12/1940 Keller 431/115 X 2,658,742 11/1953 Suter et a1 263/32,795,054 6/1957 Bowen 263/3 X Primary ExaminerEdward G. FavorsAttorneys-James R. Hoatson, Jr. and Philip T. Liggett l Optional FreshSlack l l l I r:.:i J

Curing Zone /7 THERMAL INCINERATION UNIT The present invention relatesto an improved form of thermal incinerator unit and in particular to atype adapted for use with a drying oven or a curing zone discharging anair-polluting gas stream containing combustible components of highB.t.u. content.

In accomplishing thermal incineration of combustible waste productsthere is generally provided the direct emission of flame and hot gasesinto the waste gas stream. In addition, there should be provided thecustomary three elements of good combustion, i.e., time, temperature andturbulence. For high-efficiency incineration systems, there have beenvarious recouperative"d designs which embody heat exchange means 5 thatwill transfer heat from the hot combustion gases to the incoming wastegas stream; however, such designs are not necessarily adaptable todrying oven systems where it is desired to reheat and recycle a portionof the waste gas stream to the oven zone. Also, there may be a problemin the handling of the high B.t.u. content gas stream in many of theconventional incinerator units by reason of producing an excessivetemperature rise through the length of the combustor section of theunit.

It may, therefore, be considered an object of the present invention toprovide a thermal incineration unit, particularly for combination with adrying oven, such that there is provided means to dilute the incomingcombustible material in the contaminated stream and thereby increase theeffective inlet temperature" of such stream while, at the same time,reducing the temperature rise through the combustor section to therebyhold to a given maximum temperature at the outlet of the incinerator.

It may be considered a further object of the invention to provide aunitary oven-incinerator design which provides for the special blendingin of heated gas at the inlet or burner and of the incinerator sectionsuch that combustion of fumes in the gas stream will be initiated with aminimum of fuel from a burner.

A still further object of the present invention is to provide an overallunitary oven-incinerator design which will provide a gas recirculationflow from and back to the oven as well as gas flows through theincinerator section and to gas bypass sections.

In a broad aspect, the present invention provides a thermal incineratorunit for use in combination with a curing zone discharging combustiblefumes, which comprises in combination, an elongated combustion sectionwith a fume inlet opening at one end and a hot gas outlet from theopposite end thereof, an axial-positioned burner means directed intosaid inlet opening and adjustable fuel supply means to said burnermeans, gas passageway means from said hot gas outlet to said fume inletopening to effect a hot gas recycle to the latter at said burner means,additional gas passageway means from said hot gas outlet to the curingzone, and a gas outlet conduit from said hot gas outlet to effect acleaned gas discharge to the atmosphere, at least one adjustable freshair inlet means to said unit, and fan means connective with said unitproviding flow of fumes into said combustion section and through saidpassageway and conduit means to maintain gas and fume flowstherethrough.

As noted hereinbefore, the present improved design is particularlyadapted to accommodate high B.t.u. content fumes so as to effect anefficient incineration of the fumes while precluding an excessivetemperature rise through the cornbustion zone. For example, because ofthe limitations of the metal enclosure comprising the combustionsection, it may be undesirable to have a temperature which is greaterthan about l,350 to [400 F. As a result, the present design andarrangement provides for a recycle of hot combustion gases from theoutlet zone of the combustor section back along the latter and into itsinlet end in admixture with the fume stream being introduced thereto.Where the fume stream is at relatively low temperature, of the order ofabout 500 F., there can be burner means to effect a preheating of thisstream; however, unless a large quantity of burner fuel is utilized, itis difficult to effect the initiation of the incineration of the fumes,and even with preheat to effect oxidation, there will be a temperaturerise of some 800 F. to reach a l,350 F. temperature at the outlet end ofthe unit. Thus, by providing recycle gases, which are at the 1,350" F.temperature level, into admixture with the fume-laden stream, there canbe a resulting mixture of the order of at least about l,050 F., wherebyincineration can be started and there will be a lessened temperaturedifferential through the combustion section with better operatingefficiency.

In a preferred design of the incinerator section, the hot recycle gaseswhich are to be brought into admixture with the fume stream will bereturned through an annular-form passageway which is in an indirect heatexchange relationship with the outer wall of the combustion section sothat there is a maximum retention of heat in the system. Also,preferably, there will be utilized a heat exchange zone at thedownstream end of the combustion section so that fresh air may be heatedby indirect heat exchange means from the incinerated fumes leaving thecombustion section. The heated fresh air together with a portion of theincinerated gas stream and, where desired, a portion bypassed fumestream, may be passed through suitable conduit means to the curing zoneor drying oven from which the fume stream is withdrawn.

in a simplified construction and design arrangement, there may beutilized a single fan to effect the withdrawal of fumes from a curingzone and the introduction of the fumes into the combustor zone, as wellas induce hot gas flow trough the recycle passageway and combined heatedgas flow back into the curing zone or oven. Of course, where desired,additional fan means may be brought into use in connection with theintroduction of fresh air or to effect increase flow rates with respectto recycle and gas bypass passageway means.

In a more elaborate construction and design arrangement, there may beincorporated a fume bypass passageway around or in a heat exchangerelationship with the hot recycle stream passing back around thecombustor zone such that recirculated gas may be carried back to theoven or curing zone in admixture with a portion of the oxidized gasstream. The bypass arrangement permits a controlled portion of thefume-laden gas stream to be introduced into the combustor zone such thatthere may be a short residence period in such zone, say of the order of0.1 to 0.2 seconds to produce of the order of per-' cent conversion.However, an extended passageway from the combustor zone can permit agreater residence time for the net oxidized gas stream carrying to thedischarge stack such that there is atleast about 0.5 to 0.6 seconds ofresidence time to produce a greater than percent conversion and anefficient air-pollution control arrangement.

The recycle of a portion of the hot combustion gases from the end of thecombustor zone has the effect of increasing the effective inlettemperature at a substantially constant outlet temperature operationand, of course, this reduces the fuel requirements for the burner meansat the inlet means of combustor zone. In still another aspect, therecycle arrangement provides for the admixture with the combustible fumestream being introduced to the incineration zone to effect an increasedtemperature for such stream and a reduction in the temperature rise ofthe gas stream carrying through the length of the combustion zone.Stated another way, the practical result of the incinerator design is toprovide a unit that can provide high efficiency and a controlled maximumoutlet temperature which is particularly adapted for use in combinationwith a drying oven or other type curing zone which discharges a fumestream with a high B.t.u. content.

Reference to the accompanying drawing and the following descriptionthereof will serve to set forth the improved incinerator design andconstruction, as well as point out additional advantageous featureswhich may be obtained from the use thereof in connection with theincineration of high B.t.u.

content gases.

FIG. 1 of the drawing is a schematic elevational view indicating athermal incinerator system providing for hot gas recycle in combinationwith a curing zone.

FIG. 2 of the drawing is a diagrammatic side elevational view of analternate form of a thermal inciner-ator unit providing for both recyclegas passageway and fume bypass passageway means which encompass thecombustor section of the unit in a heat exchange manner.

FIG. 3 of the drawing is a partial elevational view indicating amodified system for effecting the stagewise introduction of the hotrecycle gases into the combustor section of the unit.

Referring now particularly to FIG. 1 of the drawing, there is indicateda thermal incinerator unit having a combustor zone which is encompassesby shell means 2 with an inlet opening 3, formed from baffle plate means4, and an outlet section 5 connecting with a stack means 6. There isalso indicated the use of a gas passageway tubes 7 providing a heatexchange zone 8 therearound to accommodate the heating of a freshairstream that is introduced by way of inlet means 9. The latter, inturn, has a damper means 10 therein to control fresh airflow into thesystem. Upstream of the inlet portion of the combustor section there isalso provided a mixing section 11 which is in communication with fanmeans 12 that, in turn, receive a fume-laden stream from duct means 13and fresh air from duct means [4. The latter is provided with a damperor valving means 15 to effect the control of the quantity of fresh airbeing introduced into the system at this zone.

There is also indicated diagrammatically in FIG 1 of the drawing a smalldrying oven or curing zone 16 encompassed by housing means 17 adapted toaccommodate the movement of wires or other coated items that are passedthrough such curing zone. A fume-laden gas outlet passageway from thecuring zone is provided at outlet means 18 to connect to duct means 13and thence pass by way of fan 12 around the burner means 19 and into thethermal incinerator section of the unit. The burner 19 is indicated asbeing supplied with fuel by way of line 20 and control valve means 21.

The downstream end of the combustor section 1 is provided with asidewall hot gas opening 22 which is connective with a recyclepassageway 23 as well as with a recirculation passageway 24 whichconnects with and discharges into curing zone 16. The recirculationpassageway 24 also is in open communication with the heat exchange zone8 for the fresh air being introduced by way of inlet means 9, whereby aresulting mixed gas stream of combustion products are preheated air willbe introduced back into the curing zone.

As a still further feature of the present design, there is indicated abypass passageway 25 connective with the fume or combustor inlet zone 11whereby a portion of the fume-laden gas stream from fan means 12 cancarry around combustor I and directly back to the curing zone inadmixture with preheated fresh air and hot combustion gases from outletmeans 22. In other words, the bypass arrangement precludes having topass all of the fume stream through the combustor zone 1 and permits acontrolled incineration operation with only a desired portion of thetotal gas stream having to be discharged as net gas through the stackmeans 6. Further advantages of the bypass arrangement provide for thepresent improved system of having a controlled temperature rise in theincinerator section, while also providing for the blending of thevarious gas stream, particularly as to quantity and temperature, forrecirculation into the curing zone. A damper 25 can assist in flowcontrol.

Referring now to H0. 2 of the drawing, there is indicated a modifiedform of incineration unit providing for an encompassing arrangement ofrecycle and gas bypass passageways around an internal combustion zone.Specifically, the is indicated an internal combustion zone 26 defined byshell 27 which has a gas inlet opening 28 and a downstream open enddischarge arrangement into tubular means 29 and into an outlet section30 connecting to stack means 31. A contaminated gas conduit 32 isindicated as connecting to fan means 33 and the latter discharging intoan inlet section 34 which in turn is in open communication with a mixingzone 35 leading to the combustion section inlet 28. A burner 36 is alsoshown as being positioned within the inlet passageway 28 so as toprovide controlled heat for the mixed gas stream entering combustor zone26, so as to ensure ignition of the fume-laden gas stream. In addition,burner 36 is provided with a fuel line 37 and valve means 38 so as toprovide controlled quantities of fuel thereto.

in accordance with the present invention, which provides for recycle ofhot gases at and within the incineration section, there is utilized anadditional housing or shell means 39 concentrically around shell 27 inorder to form a recycle passageway 40. Thus, hot gases from the outletend of combustor zone 26 may pass through a regulated area passageway orzone 41 into recycle passageway 40 and be deflected from the latter intothe mixing section 35 and to the combustor inlet 38 to therein becomeadmixed with the combustible fumes entering from fan means 33. As willhereinafter be more fully set forth, the recycle of hot combustion gaseswill provide an effective higher temperature mixed gas stream so as toin turn reduce the temperature rise across the length of the combustionsection in zone 26. For example, where the solvent or fume laden gasstream is of the order of 500 F. and below ignition temperature, theadmixture of discharged hot gases at a temperature of the order of say1,350 F. can provide, without particular aid from burner means 36, amixed gas stream temperature of the order of 1,050 F. whereby ignitionwill take place and the temperature rise through the length of thecombustible zone be held to the order of only 300 F.

In a manner similar to that shown in FIG. 1, there is a heat exchangezone built within the downstream end of the thermal incineration unit ofFIG. 2, by reason of a fresh air inlet duct means 42, with damper means43, leading into an encompassing heat exchange section 44 around gaspassageway tubes 29. Thus, a preheated fresh airstream may be admixedinto the hot gas steam entering a recirculating gas passageway 45 to inturn be transferred to a drying oven or curing zone by way of outletmeans 46.

The present embodiment also indicates the use of shell means 47 at aspaced distance around the combustor shell 27 and the recycle shell 39to provide a gas bypass passageway 48. The latter has an inlet opening49 communicating with the fan discharge section 34 and a downstreamsection which is an open communication with the recirculating gaspassageway 45 whereby a portion of the fume-laden gas stream canentirely bypass the incineration zone and be recirculated into thecuring zone, drying oven, etc., in admixture with at least a portion ofthe resulting combustion gases and controlled quantities of preheatedair.

Various types of flow control means or dampers may be used in connectionwith the various gas passageways of the thermal incinerator section andfor the recirculation to the gas bypass passageway. However, it is notintended to limit the control means to any one type valving, dampers, orregulating apparatus, or to any specific location. Diagrammatically, thepresent drawing indicates movable damper means 50 at the passageway 41so as to regulate the quantity of hot gases that may be recycled inpassageway 40 and at the same time divert a portion thereof as a hot gasstream passing into the curing zone from the incinerator secton. Thereare also indicated damper means 51 at the inlet section 49 for the fumebypass 48 so as to control the quantity of gas being directlyrecirculated to the curing zone without passage into the combustor zone.As hereinbefore noted, under certain operating conditions, it may bedesirable to only pass a small portion of the fume-laden gas stream intothe combustor zone 26 and also pass a relatively small portion of theresulting hot combust gases to stack means 31.

FIG. 2, as also provided by the construction of FIG. 1, effects anextended residence chamber for the combustion section by virtue of thehot gas stream from the combustor zone 26 being connective through tubemeans 29 to an outlet section 30 which, in turn, connects with thedischarge stack,

whereby adequate time for thermal conversion of entrained fumes will beobtained to preclude air-pollution. Still further, other damper orcontrol valve means may be embodied within the design of FIG. 2, as forexample, within outlet section 30 or upstream of the heat exchange tubes29, whereby a more closely controlled gas flow can be obtained.

Actually, it is not intended to limit the present thermal incineratorunit to any predetermined volumes of gas flows within the variouspassageways and within the central combustion section inasmuch as thevolume through the incinerator or combustor zone may comprise an amountsubstantially equivalent to that for bypass passageway 48 or a quantitywhich is greater or lesser than the amount in the bypass passageway.However, in all cases, a substantial quantity of the hot combustiongases leaving the combustor zone 26 shall be recycled by way ofpassageway 40 back to the combustor inlet so as to provide the higherinlet temperature to such zone to result the desired low-temperaturedrop in the unit as well as sustain an ignition temperature for thesystem. lt is also to be noted that variations may be made with respectto heat exchange section or to the positioning of certain of the gaspassageways, inasmuch as the drawings may be merely diagrammatic in thisaspect. A preferred unit, however, provide for the heat exchangerelationship between the recycle passageway and the combustion section26, as well as a heat exchange relationship between the recyclepassageway 40 and the bypass passageway 48.

With reference to FIG. 3 of the drawing, there is indicated amodification within the shell defining the combustor zone by reason ofshell 27 providing a plurality of spaced-apart, angularly positioned gasinlet means 52 which will permit small portions of the recycle gasstream from passageway 48 to be introduced at spaced points in thecombustor zone 26 and, in effect, reduce the output from the burnermeans as well as keep the temperature rise in the combustor zone to alow differential. The openings 52 as shown are, of course, diagrammaticand can be varied as to number and as to angular relationship with thewall of the combustion zone and still be within the scope of the presentinvention.

lclaim as my invention:

1. A thermal incinerator unit for use in combination with a curing zonedischarging combustible fumes, which comprises in combination, anelongated combustion section with a fume inlet opening at one end and ahot gas outlet from the opposite end thereof, an axial-positioned burnermeans directed into said inlet opening and adjustable fuel supply meansto said burner means, gas passageway means from said hot gas outlet tosaid fume inlet opening to effect a hot gas recycle to the latter atsaid burner means, additional gas passageway means from said hot gasoutlet to the curing zone, and a gas outlet conduit from said hot gasoutlet to effect a cleaned gas discharge to the atmosphere, at least oneadjustable fresh air inlet means to said unit, and fan means connectivewith said unit providing flow of fumes into said combustion section andthrough said passageway and conduit means to maintain gas and fume flowstherethrough.

2. The thermal incinerator unit of claim 1 further characterized thatsaid gas passageway means for effecting hot gas recycle is providedannularly around said elongated combustion section and in heat exchangerelationship therewith.

3. The thermal incinerator unit of claim 1 further characterized in thata gas bypass passageway extends longitudinally coextensive with saidcombustion section and is connective between said fan means and saidadditional gas passageway means from said hot gas outlet, whereby theremay be a recirculation of a fume containing stream to the curing zonewithout passage through said combustion section.

4. The thermal incinerator unit of claim 3 still further characterizedin that said bypass passageway is in heat exchange relationship withsaid hot gas recycle passageway means.

5. The thermal incinerator unit of claim 1 further characterized in thata heat exchan e section is provided in communrcation with the hot gasout et from said combustion section and air inlet means to said heatexchange means provides for preheating air thereto, and an outlet fromsaid heat exchange section is in communication with said additional gaspassageway means to the curing zone whereby heated fresh air may beadmixed with gas from said hot gas outlet.

6. The thermal incinerator unit of claim 1 further characterized in thatflow control means are provided in combination with the hot gas outletfrom said combustion section whereby there may be regulation of the flowgases to said gas passageway means for hot gas recycle and control ofgas flow to said additional gas passageway from said hot gas outlet.

7. The thermal incinerator unit of claim 1 further characterized in thatsaid gas passageway means from said hot gas outlet to said fume inletopening is of an annular form around said elongated combustion sectionand a gas bypass passageway is provided in an annular form around saidannular form recycle gas passageway, whereby there is a resulting heatexchange relationship between said gas passageways.

8. The thermal incinerator unit of claim 7 still further characterizedin that flow control means are provided in said bypass gas passagewaywhereby to control fume flow from said fan means to said combustionsection and to said gas bypass passageway.

9. In combination with an oven of the type recirculating at least aportion of the contaminated gas stream, a thermal incineration section,comprising in combination, an elongated open-ended inner shell defininga combustion section with a fume inlet and a hot gas outlet meanstherefor, an elongated outer shell spaced around said inner shell andproviding a recycle passageway for recycle of hot gases, a fume-ladeninlet at one end of said outer shell in alignment with the open gasinlet to said inner combustion sections, a fume passageway from saidoven to said fume inlet of said combustion section, a burner with fuelsupply means thereto positioned centrally within said fume inlet to thelatter, an incinerated gas outlet from said outer shell, additional wallmeans spaced adjacent said outer shell to provide a gas bypass sectiontherearound which is in heat exchange relationship with said outershell, 3 return passageway means from said bypass section to said oven,and a blower means within said fume passageway to maintain gas flow andgas recirculation within said incineration section and said gas bypasssection.

10. The combined oven-thermal incineration section of claim 9 furthercharacterized in that adjustable flow control means is provided withineach of said gas passageways and said gas bypass sections, whereby thevolume of gas flow can be regulated within each portion of saidincineration section.

1. A thermal incinerator unit for use in combination with a curing zonedischarging combustible fumes, which comprises in combination, anelongated combustion section with a fume inlet opening at one end and ahot gas outlet from the opposite end thereof, an axial-positioned burnermeans directed into said inlet opening and adjustable fuel supply meansto said burner means, gas passageway means from said hot gas outlet tosaid fume inlet opening to effect a hot gas recycle to the latter atsaid burner means, additional gas passageway means from said hot gasoutlet to the curing zone, and a gas outlet conduit from said hot gasoutlet to effect a cleaned gas discharge to the atmosphere, at least oneadjustable fresh air inlet means to said unit, and fan means connectivewith said unit providing flow of fumes into said combustion section andthrough said passageway and conduit means to maintain gas and fume flowstherethrough.
 2. The thermal incinerator unit of claim 1 furthercharacterized that said gas passageway means for effecting hot gasrecycle is provided annularly around said elongated combustion sectionand in heat exchange relationship therewith.
 3. The thermal incineratorunit of claim 1 further characterized in that a gas bypass passagewayextends longitudinally coextensive with said combustion section and isconnective between said fan means and said additional gas passagewaymeans from said hot gas outlet, whereby there may be a recirculation ofa fume containing stream to the curing zone without passage through saidcombustion section.
 4. The thermal incinerator unit of claim 3 stillfurther characterized in that said bypass passageway is in heat exchangerelationship with said hot gas recycle passageway means.
 5. The thermalincinerator unit of claim 1 further characterized in that a heatexchange section is provided in communication with the hot gas outletfrom said combustion section and air inlet means to said heat exchangemeans provides for preheating air thereto, and an outlet from said heatexchange section is in communication with said additional gas passagewaymeans to the curing zone whereby heated fresh air may be admixed withgas from said hot gas outlet.
 6. The thermal incinerator unit of claim 1further characterized in that flow control means are provided incombination with the hot gas outlet from said combustion section wherebythere may be regulation of the flow gases to said gas passageway meansfor hot gas recycle and control of gas flow to said additional gaspassageway from said hot gas outlet.
 7. The thermal incinerator unit ofclaim 1 further characterized in that said gas passageway means fromsaid hot gas outlet to said fume inlet opening is of an annular formaround said elongated combustion section and a gas bypass passageway isprovided in an annular form around said annular form recycle gaspassageway, whereby there is a resulting heat exchange relationshipbetween said gas passageways.
 8. The thermal incinerator unit of claim 7still further characterized in that flow control means are provided insaid bypass gas passageway whereby to control fume flow from said fanmeans to said combustion section and to said gas bypass passageway. 9.In combination with an oven of the type recirculating at least a portionof the contaminated gas stream, a thermal incineration section,comprising in combination, an elongated open-ended inner shell defininga combustion section with a fume inlet and a hot gas outlet meanstherefor, an elongated outer shell spaced around said inner shell andproviding a recycle passageway for recycle of hot gases, a fume-ladeninlet at one end of saId outer shell in alignment with the open gasinlet to said inner combustion sections, a fume passageway from saidoven to said fume inlet of said combustion section, a burner with fuelsupply means thereto positioned centrally within said fume inlet to thelatter, an incinerated gas outlet from said outer shell, additional wallmeans spaced adjacent said outer shell to provide a gas bypass sectiontherearound which is in heat exchange relationship with said outershell, a return passageway means from said bypass section to said oven,and a blower means within said fume passageway to maintain gas flow andgas recirculation within said incineration section and said gas bypasssection.
 10. The combined oven-thermal incineration section of claim 9further characterized in that adjustable flow control means is providedwithin each of said gas passageways and said gas bypass sections,whereby the volume of gas flow can be regulated within each portion ofsaid incineration section.